A snow fence is any barrier used to protect an area from wind-transported snow. Controlling blowing snow can reduce snow removal costs, improve highway safety, and improve the distribution of snow for recreation, agriculture, and water development.
Blowing snow contributes to hazardous driving conditions by reducing visibility and causing the formation of slush and ice. Snowdrifts add to snow removal costs, but this aspect is trivial compared to the safety hazards caused by drifts. Snowdrifts can cause loss of vehicle control, reduced sight distance on curves, impair motorist visibility by increasing the concentration of snow particles at eye-level, promote ice formation, provide a barrier preventing maneuvers for collision avoidance, and render safety barriers ineffective. In addition, snowdrifts provide a source of water that can infiltrate under the pavement and cause damage to the road surface.
The first written reference to snow fences appeared in a book published in Norway in 1852. Probably the first fences in the U.S. were used along the Union Pacific Railroad in Wyoming where, by 1880, "innumerable" fences were reported to be in place. The 1930's saw widespread use of snow fences to protect roads.
After World War II, however, inexpensive fuel and improvements in snow removal equipment favored a "brute force" approach in dealing with snowdrifts. As a result, interest in snow fences and over the next 20 years or so, with very little effort made to improve passive drift control methods. In addition, snow fences were seldom as effective as they could have been because guidelines for their use were inadequate. In some cases, improperly placed fences caused more problems than existed before fencing.
The turning point for snow fences was in the early 1970's, when new guidelines were used to design a $2 million snow fence system to protect a section of Interstate Highway-80 (I-80) in Wyoming. The remarkable effectiveness of those fences in eliminating drifts and reducing accidents, provided irrefutable evidence that properly designed snow fences could work.
Although actual costs vary widely, mechanical snow removal typically costs about $3 per ton. By comparison, the cost of storing snow with fences average about 1/100th as much, or $0.03 per ton. As an example, an 8 foot tall snow fence typically costs less than $8 per foot ($25/m) to build, including easement costs. When filled to capacity, such a snow fence will store about 20 tons of snow per foot of length. Assuming the fence lasts 25 years without maintenance, the cost of storing snow would therefore be less than $0.02/ton.
By reducing the quantity of snow arriving at the road, snow fences can dramatically improve motorist visibility and reduce the formation of slush and ice. A 10-year study of the I-80 snow fence system in Wyoming, published in the Transportation Research Record in 1982, showed that fences eliminated drift formation at all locations where they were used, reducing winter maintenance costs by at least one-third. Accidents in blowing snow conditions were reduced in proportion to the extent of snow fence protection. Fencing one-half of a 62-mile section of this highway was found to prevent 54 accidents and 35 injuries over a winter having average snowfall and traffic volume, with the result that the original construction cost of the fences could be amortized in less than 15 years by the savings in property damage alone.
The evidence of how effective snow fences can be is irrefutable. It is therefore incumbent on public officials to apply this technology to improve the safety and convenience of the public; however, this technology has not been widely applied for the following reasons:
1. Lack of tall portable fences.
To be effective, fences must be at least 6 feet tall, and preferably taller. In many areas, permanent snow fences cannot be used because of conflicts with other land uses, and tall portable fences have not been considered feasible because of the more expensive supports required to withstand strong winds. Using conventional fence materials, installing, removing and storing tall fences on an annual basis is prohibitively expensive and otherwise impractical Fences taller than 5 feet or so require sturdy vertical supports such as 5-inch diameter wood posts on 8-foot centers embedded at least 3 feet or more in the ground, or guyed steel T-posts. In addition, the wind loads on taller fences require more elaborate methods of attaching the fencing material to the supports. Although 6-foot wide plastic fencing material has been marketed by at least one manufacturer, it is seldom used because of the aforementioned installation problems.
Existing fence designs do not lend themselves to economical temporary installations. Disadvantages include 1) expensive materials, 2) time-consuming installation, and 3) excessive disturbance to the site.
2. Excessive maintenance costs.
Plastic fencing materials are convenient to handle and store, and cost less than some wood-based designs. Although plastic materials can also be more durable, they are easily damaged when improperly installed. To last, plastic materials must be immobilized at supports to prevent abrasion. Proper attachment using conventional fence supports is expensive and time consuming.
3. Poor performance.
The advantages of plastic fencing materials are offset by their tendency to cause snow to be deposited in the immediate vicinity of the fence; an effect resulting from the small openings that make up the open area. Snow deposition at the fence reduces the effective fence height, and snow settlement causes the plastic fencing to sag between vertical supports. Because the storage capacity of a fence is proportional to the 2.2 power of the fence height, a loss of 6 inches reduces the capacity of a 6-foot tall fence by 18%. Snow settlement also damages the fencing material.